- Season
- Available year-round, with peak quality in cool spring and autumn months.
- Price
- Low
- Nutrition per 100 g
- 17 kcal
- 1.2 g protein
- 0.3 g fat
- 3.2 g carbs
Romaine Lettuce
Vegetables
Romaine Lettuce
Romaine lettuce, also known as cos lettuce, is a long-headed variety of Lactuca sativa distinguished by its upright growth, sturdy central rib, and leaves that graduate from pale, aqueous interiors to darker, more robust exteriors.
In practice
How to store
- On the counter
Not recommended, as romaine rapidly loses turgor and sweetness at room temperature.
- In the fridge
Store unwashed heads loosely wrapped in a breathable bag in the crisper drawer for up to 7 days.
- In the freezer
Freezing is unsuitable for fresh use, though blanched romaine may be frozen for cooked applications such as soups.
How to choose
Choose romaine heads that feel heavy for their size, with tightly packed hearts and crisp leaves. The exterior should be free from russet spotting or excessive browning at the margins, while the cut base should appear moist and pale rather than oxidized.
What to swap in
Best swap
Little gem lettuce, which offers a similar crunch and mild bitterness in a smaller format.
In a pinch
Iceberg lettuce, acknowledging its inferior aromatic complexity but comparable crispness.
Preparation
Separate leaves gently, wash in abundant cold water to dislodge grit from the ribs, and dry thoroughly. For classic preparations, tear rather than cut to minimize oxidative browning along the edges.
Don't toss it
Reserve the tougher outer leaves and cores for green stocks or for blending into savory juices, where their bitterness adds structure.
In the kitchen
Cooking
While most celebrated raw, romaine tolerates heat with surprising dignity. Halved heads may be grilled or seared, where the exterior chars and sweetens while the heart retains crunch, a technique that underscores its structural resilience.
Goes well with
- Anchovy
- Garlic
- Parmesan
- Lemon
- Olive Oil
- Grilled Meats
What it is
Romaine lettuce, also known as cos lettuce, is a long-headed variety of Lactuca sativa distinguished by its upright growth, sturdy central rib, and leaves that graduate from pale, aqueous interiors to darker, more robust exteriors.
How it tastes
The flavor profile of romaine lettuce unfolds with a cool, aqueous attack, immediately refreshing and faintly bitter. The mid-palate reveals a grassy sweetness and subtle mineral salinity concentrated in the ribs, while the finish is clean, faintly tannic, and drying, a quality that allows it to carry assertive dressings without collapse.
Common questions
Is romaine lettuce more nutritious than other lettuces?
Can romaine lettuce be cooked?
Deep dive
3 min read
Varieties
Though often treated as a monolith, romaine lettuce encompasses a family of cultivars bred for different climates and uses.
Parris Island Cos
Developed in the United States (released in the early 1950s from breeding work in South Carolina) for uniformity and disease resistance, this variety thrives in temperate coastal climates. Harvested at full maturity, it offers pronounced rib crunch and a balanced bitterness suited to classic salads.
Valmaine
Bred for warmer regions, Valmaine tolerates heat without bolting, developing darker outer leaves rich in chlorophyll. The flavor is more assertive, with a distinctly herbal mid-palate and a slightly bitter finish.
Little Gem
A compact semi-cos cultivar that matures at a small size, often harvested by hand, with sweetness concentrated in its tightly bound heart. It is typically grown in well-drained soils.
Across these types, harvest is typically conducted in the early morning to preserve cellular pressure. Flavor nuance is inseparable from soil composition, irrigation restraint, and the timing of the cut, all of which determine whether romaine reads as merely crisp or quietly complex.
History
The story of romaine lettuce spans millennia and mirrors the movement of agriculture itself.
Ancient era
Lettuce was known to the Egyptians as early as 2700 BCE, depicted in tomb paintings as a sacred plant associated with fertility. The Greeks and Romans cultivated elongated lettuces resembling modern romaine, valuing them both as food and medicine. Roman writers, including Pliny the Elder, recorded lettuce's reputation as cooling and sleep-inducing, and the poet Martial noted that lettuce, once served at the end of meals, had come to open them.
Medieval era
As monastic gardens preserved horticultural knowledge, cos-type lettuces traveled along Mediterranean trade routes. The name "cos" is traditionally linked to the Greek island of Kos, suggesting a locus of refinement and dissemination. Medieval cooks appreciated its bitterness as a counterpoint to rich, spiced dishes common to the period.
Modern era
Romaine achieved canonical status in the twentieth century with the codification of Caesar salad, anchoring it in both popular and haute cuisines. Industrial agriculture standardized its form, yet contemporary growers have revived older cultivars, reasserting regional identity and seasonality in what was once a purely utilitarian leaf.
Science
Romaine lettuce owes its texture to a high proportion of cellulose in the ribs, balanced by thin-walled parenchyma cells in the leaf blade. Bitterness arises from sesquiterpene lactones, compounds that increase with leaf maturity and environmental stress. Chlorophyll concentration in darker leaves correlates with higher micronutrient density, explaining the nutritional gradient from heart to exterior.
Sourcing and ethics
Ethical sourcing of romaine centers on water use, labor conditions, and food safety. As a water-intensive crop often grown in arid regions, responsible producers employ drip irrigation and soil moisture monitoring. Fair labor practices remain critical, particularly during hand harvest. Recent food safety concerns have underscored the importance of traceability and regional diversification, encouraging consumers to seek locally grown romaine when possible.